Morphodynamical Response of Small Rivers to Large-Scale Waterway Projects

With the development of inland navigation, small rivers have the demand for the construction of large-scale waterways. Taking the reach from Likou to Binlangtan of the Dongjiang River in China as an example, this paper analyzes the erosion and deposition process of the four shoals in this reach over the last 20 years; establishes a physical model dominated by the movement of the bed load for this reach; and utilizes this physical model to study the morphodynamical response of small rivers to large-scale waterway projects. The main conclusions are as follows: (1) the erosion and deposition process in the Dongjiang River can be divided into three stages: natural erosion and deposition equilibrium stage, generalized riverbed undercutting stage, and the self-adaptive adjustment stage. (2) Under the action of the large-scale waterway projects, decreasing of water levels caused by dredging can be remedied by adjusting the navigation channel bed elevation; local adverse flow caused by spur dike can be remedied by sealing the sand mining pit and shortening the dike head; the suction problem, caused by the navigable branch, can be remedied by adopting a compound channel section with multiple steps. (3) A new river regime is reshaped by waterway regulation spur dikes, and a new erosion and deposition state is formed. The layout of the navigation channels should follow the reshaped regime to reduce sediment deposition and ensure the navigation depth. This paper provides technical support for the construction of large-scale waterways in small rivers.